1. Field of the Invention
The present invention relates to a solder suitable for joining sintered metal parts, especially sintered iron parts, to each other, and also to a soldering method for said solder.
2. Description of the Prior Art
Heretofore, it has been believed to be difficult to join sintered metal parts to each other by soldering because the molten solder infiltrates into the pores of the sintered body and the solder does not stay on the joining area. Recently, however, there has been developed a new solder which permits the soldering of sintered iron parts, and it is attracting public attention. This solder is a powder of an alloy composed of Ni 40 wt%, Cu 40 wt%, and Mn 20 wt%. It is characterized by that as the molten solder infiltrates into the pores of the sintered body, it solidifies immediately upon reaction with iron in the sintered body, preventing the molten solder from infiltrating into the sintered body any more. (Refer to Zairyo Kagaku (Material Science), Vol. 21, No. 3, 162, and Kinzoku (Metals), Vol. 52, No. 1, 1982, 68.)
The above-mentioned Ni-Cu-Mn solder, however, is still subject to infiltration, although less than conventional ones, and has a disadvantage that the reaction with iron wastes the solder and causes dimensional changes. For this reason, the solder is regarded to be less economical and reliable.